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[thirdparty/man-pages.git] / man2 / kexec_load.2

.\" Copyright (C) 2010 Intel Corporation
.\" Author: Andi Kleen
.\"
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.TH KEXEC_LOAD 2 2012-07-13 "Linux" "Linux Programmer's Manual"
.SH NAME
kexec_load \- load a new kernel for later execution
.SH SYNOPSIS
.B #include <linux/kexec.h>
.br
.BI "long kexec_load(unsigned long " entry ", unsigned long " nr_segments ","
.br
.BI "                struct kexec_segment *" segments \
", unsigned long " flags ");"

.IR Note :
There is no glibc wrapper for this system call; see NOTES.
.SH DESCRIPTION
The
.BR kexec_load ()
system call loads a new kernel that can be executed later by
.BR reboot (2).
.PP
The
.I flags
argument is a mask whose high-order bits control the operation of the call.
The following values can be specified in
.IR flags :
.TP
.BR KEXEC_ON_CRASH " (since Linux 2.6.13)"
Execute the new kernel automatically on a system crash.
.\" FIXME figure out how this is really used
.TP
.BR KEXEC_PRESERVE_CONTEXT " (since Linux 2.6.27)"
Preserve the system hardware and
software states before executing the new kernel.
This could be used for system suspend.
This flag is only available if the kernel was configured with
.BR CONFIG_KEXEC_JUMP ,
and is only effective if
.I nr_segments
is greater than 0.
.PP
The low-order bits of
.I flags
contain the architecture of the to-be-executed kernel.
Specify (OR) the constant
.B KEXEC_ARCH_DEFAULT
to use the current architecture,
or one of the following architecture constants
.BR KEXEC_ARCH_386 ,
.BR KEXEC_ARCH_X86_64 ,
.BR KEXEC_ARCH_PPC ,
.BR KEXEC_ARCH_PPC64 ,
.BR KEXEC_ARCH_IA_64 ,
.BR KEXEC_ARCH_ARM ,
.BR KEXEC_ARCH_S390 ,
.BR KEXEC_ARCH_SH ,
.BR KEXEC_ARCH_MIPS ,
and
.BR KEXEC_ARCH_MIPS_LE .
The architecture must be executable on the CPU of the system.

The
.I entry
argument is the physical entry address in the kernel image.
The
.I nr_segments
argument is the number of segments pointed to by the
.I segments
pointer.
The
.I segments
argument is an array of
.I kexec_segment
structures which define the kernel layout:
.in +4n
.nf

struct kexec_segment {
    void   *buf;        /* Buffer in user space */
    size_t  bufsz;      /* Buffer length in user space */
    void   *mem;        /* Physical address of kernel */
    size_t  memsz;      /* Physical address length */
};
.fi
.in
.PP
.\" FIXME elaborate on the following:
The kernel image defined by
.I segments
is copied from the calling process into previously reserved memory.
.SH RETURN VALUE
On success,
.BR kexec_load ()
returns 0.
On error, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EBUSY
Another crash kernel is already being loaded
or a crash kernel is already in use.
.TP
.B EINVAL
.I flags
is invalid; or
.IR nr_segments
is too large
.\" KEXEC_SEGMENT_MAX == 16
.TP
.B EPERM
The caller does not have the
.BR CAP_SYS_BOOT
capability.
.SH VERSIONS
The
.BR kexec_load ()
system call first appeared in Linux 2.6.13.
.SH CONFORMING TO
This system call is Linux-specific.
.SH NOTES
Currently, there is no glibc support for
.BR kexec_load ().
Call it using
.BR syscall (2).
.PP
The required constants are in the Linux kernel source file
.IR linux/kexec.h ,
which is not currently exported to glibc.
.\" FIXME Andi submitted a patch for this.
.\" Check if it got accepted later.
Therefore, these constants must be defined manually.

This system call is only available if the kernel was configured with
.BR CONFIG_KEXEC .
.SH SEE ALSO
.BR reboot (2),
.BR syscall (2)